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i ISO

Appendix. VL

steadily, but without undue forcing, for 10 or 15 minutes,
there is nothing left but a little ash, say between 2% and 5%
of the coal weight. The rise of temperature is then noted, and
a simple proportion calculation will shew the heat units per Ib.
of coal, or calorific value. It is best that the range of tem-
perature should lie equally on each side of the atmospheric
temperature, and thus automatically allow for radiation.

The Dowson Gas Calorimeter, Fig. 1018, is essentially a
small boiler, to which the whole heat of combustion of a gas flame,
as near as may be, is transferred and measured. The cylinder A
encloses the chambers B and c, which are mutually connected by

a number of concentric cylinders D. The gas, being lit in the
burner r, its products of combustion pass up through G, and down
by the cylindrical spaces to c, the condensation water emerging
at E. Water entering the boiler by the pipe M, and leaving by R,
is measured in the beaker jar u j while the gas burnt is measured
by the meter j, to the decimals of a cubic foot. Finely adjustable